Electronic ballasts for gas discharge lamps are generally known in the art. Many prior art electronic ballasts that perform both power factor correction and inverter functionality include three or more power switches (in the form of transistors). Because the cost of transistors is relatively high, reducing the number of transistors may have a significant effect on the cost of the ballast.
Electronic ballast topologies using only a single transistor have been proposed. Imposing multiple tasks upon one transistor, however, gives rise to other problems and concerns. In particular, when such a transistor turns off, voltage across the transistor can rise greatly, therefore necessitating either the use of relatively expensive transistors that are able to withstand the voltage stresses imposed, or some form of protective circuit. Unfortunately, though effective to protect the transistor from excessive voltages, such snubber circuits are themselves relatively inefficient, and dissipate large quantities of heat.
Accordingly, a need exists for an electronic ballast that has the benefits of a one transistor topology without requiring either inefficient protection techniques or relatively expensive transistors.